An Etymological Dictionary of the German Language/Annotated/flößen
flößen, flötzen, verb, ‘to float (timber), skim (milk),’ from Middle High German vlœȥen, vlœtzen, ‘to cause to flow, wash down (soil),’ factitive of fließen. The Middle High German forms with ȥ and tz correspond to those of heißen, reißen (Middle High German heiȥen-heitzen, reiȥen-reitzen), and are based upon a Gothic inflexion flautja, flauteis, since tj leads, through the medium of tt, to High German tz, but t without j to ȥ.